title: Perchlorate reduction from a highly contaminated groundwater in the presence of sulfate-reducing bacteria in a hydrogen-fed biofilm.
abstract: We used a hydrogen (H2 )-based biofilm to treat a groundwater contaminated with perchlorate (ClO(4)(-) ) at ~10 mg/L, an unusually high concentration. To enhance ClO(4)(-) removal, we either increased the H2 pressure or decreased the electron-acceptor surface loading. The ClO(4)(-) removal increased from 94% to 98% when the H2 pressure was increased from 1.3 to 1.7 atm when the total acceptor surface loading was 0.49 g H2 /m(2)  day. We then decreased the acceptor surface loading stepwise from 0.49 to 0.07 g H2 /m(2) day, and the ClO(4)(-) removal improved to 99.6%, giving an effluent ClO(4)(-) concentration of 41 µg/L. However, the tradeoff was that sulfate (SO(4)(2-) ) reduction occurred, reaching 85% conversion at the lowest acceptor surface loading (0.07 g H(2) /m(2) day). In two steady states with the highest ClO(4)(-) reduction, we assayed for the presence of perchlorate-reducing bacteria (PRB), denitrifying bacteria (DB), and sulfate-reducing bacteria (SRB) by quantitative polymerase chain reaction (qPCR) targeting characteristic reductases. The qPCR results documented competition between PRB and SRB for space within the biofilm. A simple model analysis for a steady-state biofilm suggests that competition from SRB pushed the PRB to locations having a higher detachment rate, which prevented them from driving the ClO(4)(-) concentration below 41 µg/L.
authors.affiliation: Swette Center for Environmental Biotechnology, Biodesign Institute, Arizona State University, 1001 South McAllister Ave. Tempe, Arizona, 85287-5701; School of Sustainability, Arizona State University, Tempe, Arizona.
authors.forename: Aura
authors.initials: A
authors.lastname: Ontiveros-Valencia
authors.forename: Youneng
authors.initials: Y
authors.lastname: Tang
authors.forename: Rosa
authors.initials: R
authors.lastname: Krajmalnik-Brown
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
mesh_terms: D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D018407:Bacterial Physiological Phenomena; D018441:Biofilms / Q000254:growth & development*; D058448:Biota; D001711:Biotransformation; D060587:Groundwater / Q000737:chemistry / Q000382:microbiology*; D006859:Hydrogen / Q000378:metabolism*; D010084:Oxidation-Reduction; D010472:Perchlorates / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013431:Sulfates / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D010472:Perchlorates; D013431:Sulfates; D014874:Water Pollutants, Chemical; D006859:Hydrogen; C494474:perchlorate
keywords: biofilm detachment; groundwater remediation; microbial community; perchlorate reduction; qPCR; sulfate reduction